Device for changing direct current potentials to alternating current potentials



Jan. 9, 1934. D. H. MITCHELL DEVICE FOR CHANGING DIRECT CURRENT POTENTIALS TO ALTERNATING CURRENT POTENTIALS Filed Sept. 27", 1952 lIl'lllllll PHDOJWHU dmkdm QZ da Umd OP INVENTOR o gwazd WM 71 5 fig Z, {W

g; ATTQRNEYS Patented Jan. 9, 1934 UNITED STATES PATENT OFFICE DEVICE FOR CHANGING DIRECTCURRENT POTENTIALS T ALTERNATING CURRENT POTENTIALS Application September 27, 1932 Serial No. 635,000

3 Claims. (01. 175-365) The present invention relates to devices for changing direct current potentials to alternating current potentials and, more particularly, to such devices adapted to change the potential as well 5 as the character of the current delivered thereto.

5 rnary consisting of a plurality of sections between two of which is interposed a mechanical circuit interrupter adapted periodically to make and break the primary circuit to cause an alternating current to be induced in the transformer secondary, the primary sections acting efliciently as choke coils to suppress undesirable high frequency components.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction combination of elements, and arrangement of parts, which will be exemplifled in the construction hereinafter set forth and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawing, in

which:

Fig. 1 is a diagrammatic view of parts of a circuit depicting the features of the present invention.

In apparatus for changing direct current potentials to alternating current potentials and, more particularly, in changing the resulting alternating current potentials to direct current potentials at voltages different from that of the input direct current, for example, the relatively high 5 direct current potential for the B supply in a {radio receiver with the use of any readily avail- ,able low voltage source such as a storage battery,

.4 many difliculties have been encountered. Among these are the formation of radio-frequency interference effects that are caused by the spark or arcing of the primary interrupter which are efficiently reduced by the present invention.

In the joint application of William' P. Lear, Marvin E. Nulsen and Raymond S. Yoder, Serial No. 635,056 filed September 27, 1932, and assigned to the same assignee, an apparatus is disclosed which may be used in the production of relatively high potentials for the B supply for a radio receiver in an automobile. The portions of the circuit diagram of that apparatus which involve the present invention are diagrammatically depicted in the drawing of the present application.

A source of direct current 10, such as a 6 volt storage battery is connected to the two terminals 11 and 12 of the primary circuit 13 of the apparatus. A transformer primary is formed in a plurality of sections such as 14 and 15 shown. The outer end of section 14 is connected by wire 16 to the terminal 11 and the outer end of section 15 is connected by wire 17 to the terminal 12. The inner ends of sections 14 and 15 are respectively connected by the wires 13 and 19 to a mechanical interrupter 20 of any suitable type such as the series connected magnetic interrupter shown.

The magnetic interrupter 20 briefly comprises a magnetic coil 21 connected between the wire 19 and the contact support 22 having a contact point 23 mounted thereon and a vibratory arm 25, preferably of electrically conductive magnetic material, carrying another contact point 24 and connected to the wire 18.

At 26 is shown the transformer core. The secondary circuit 27 is only partially shown in connection with the transformer secondary 28.

In operation the contact points 23 and 24 make contact with each other due to the resilience of the vibratory arm 25 thus allowing direct current to flow through the primary circuit 13. This results in the building up of a flux in the transformer primary 14-15 and a magnetic field about the coil 21 resulting in the attraction of'the vibratory arm 25 and the consequent separation of the contact points 23 and 24 which allows the field about the coil 21 and the flux in the transformer primary to die down. The resilience of the vibratory arm 25 then causes the contact points 23 and 24 to again make contact with each other and the cycle of operation is repeated. 7 The periodic building up and dying down of the flux in the transformer primary 14--15 induces an alternating current in the transformer secondary 28 which if desired may be rectified and smoothed out by a rectifier and filter circuit in a known manner, such as that described in the above identified application.

It has been found by test that during the above described cycle of operation the wire 17 carries radio-frequency potentials of appreciable magnitude caused by the spark or arcing of the interrupter 20 when the contact points 23 and 24 are separated. In a radio-receiver wherein the filament circuit is directly associated with the same source 10 of direct current these radiofrequency potentials set up in the radio receiver troublesome effects, that is, apparent conductive and reactive interference effects. In accordance with the present invention, these effects are reduced by the suppression of the above mentioned radiodrequency potentials by the sections 14 and E5 or" the transformer primary acting as choice coils.

It will thus be seen that the present invention attains the objects set iorth above in an efficient manner.

since certain changes may be made in the above construction and different embodiments of the invention could he made without departing from the scope :hereoi, it is intended that all matter c ained in the above description or shown in tne accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

it is also to he understood that the followclaims are intended to cover all 01' the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter 01 language, might he said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent, is:

l, a device for changing direct current potentials to alternating current potentials, the combination with a transformer secondary adapted to deliver alternating current potential to any desired device, of a primary circuit including a source of direct current potential, a transformer primary split into a plurality of sections, and a mechanical circuit interrupter interposed between two adjacent sections of said primary 2. In a device for changing direct current potentials to alternating current potentials, the combination with a transformer secondary adapted to deliver alternating current potential to any desired device, of a primary circuit including a source of direct current potential, a transformer primary split into two sections, a mechanical circuit interrupter interposed between the adjacent ends of said primary sections with the remaining end of each section connected into said primary circuit.

3. In a device for changing direct current potentials to alternating current potentials, the combination with a transformer secondary adapted to deliver alternating current potential to any desired device, of a primary circuit comprising a source of direct current potential, a transformer primary consisting of two sections, and a magnetic interrupter connected in series with said sections between the adjacent ends thereof.

DONALD E. MITCHELL. 

